In existing electrical connector assembly, for example, U.S. Pat. No. 6,146,181 (corresponding to Taiwanese Patent Application No.TW88119860) discloses a locking electrical connector for locking a plug and a header together. The locking electrical connector has interlocking portions for fixing the plug to the header. Specifically, when the plug and header are connected, the plug is mounted in a travel direction of pins, the pins are received by electrical contact portions respectively via openings of the header and plug. First interlocking portions positioned on a first side of the plug are interlocked with corresponding interlocking portions on a first surface of the header. The first interlocking portions of the plug comprise cams or other similarly shaped protruding members which are received by corresponding receiving portions (on the first surface of the header). Similarly, a second interlocking portion of the header interlocks with a second interlocking portion of the plug.
However, the interlocking structure of the abovementioned locking electrical connector has no function of guiding-positional limiting, therefore, when the plug is inserted into the header, it is easy to improperly insert due to misalignment.